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[1] V. Agarwal and A. K. S. Bhat, "Large signal analysis of the lcc-type parallel resonant converter using discrete time domain modeling," IEEE Transactions on Power Electronics, vol. 10, no. 2, pp. 222-238, 1995. A discrete time domain model for the LCC-type parallel resonant converter has been derived. This model has been used to predict the large signal behavior of the converter. The peak component stresses and the dynamic response of the key state variables, as obtained from the large signal analysis, using PRO-MATLAB software are plotted. SPICE results are included to verify the analytical results. Experimental results are also presented to verify the theory. [2] M. Azizur Rahman, A. R. D. Esmail, and M. A. Choudhury, "Analysis of delta pwm static ac-dc converters," IEEE Transactions on Power Electronics, vol. 10, no. 4, pp. 494-503, 1995. An analysis and implementation of delta modulation (DM) technique in the control of ac-dc converters are presented in this paper. The DM technique offers advantages of easy implementation, continuous converter voltage control, and a direct control on the line harmonics. A simple model of the delta modulator is proposed to predict switching frequency, identify dominant harmonics, and determine switching points of the converter waveforms. Results of parametric variations of the modulator and performances of the single and three phase DM converters are reported. Experimental results of the single and three phase DM ac-dc converters validate the analytical results. [3] A. K. S. Bhat, "Fixed-frequency modified series-resonant converter: Analysis, design, and experimental results," IEEE Transactions on Power Electronics, vol. 10, no. 6, pp. 766-775, 1995. It is shown that a fixed-frequency modified (LCL-type) series-resonant converter operates in five different modes with variations in the load current and the supply voltage. The converter is analyzed using the state-space approach for these operating modes. Both the general solutions and the steady-state solutions are obtained. Based on the analysis, design curves are obtained and a simple design procedure is illustrated using a design example. Detailed experimental results obtained from a MOSFET-based 500 W converter are presented to verify the analysis. It is shown that using a proper design, the converter operates only in Modes 2 and 3, ensuring a lagging power factor mode of operation for very wide variations in the load and supply voltage. [4] F. Blaabjerg, U. Jaeger, S. Munk-Nielsen, and J. K. Pedersen, "Power losses in pwm-vsi inverter using npt or pt igbt devices," IEEE Transactions on Power Electronics, vol. 10, no. 3, pp. 358-367, 1995. This paper investigates the power losses for two different IGBT technologies (Non Punch Through and Punch Through) for use in PWM-VSI inverters in order to choose the right device technology for a given application. A loss model of the inverter is developed based on experimental determination of the power losses. The loss model is used on two different modulation strategies which are a sine wave with a third harmonic added and a 60°-PWM modulation where only two inverter legs are active at the same time. The two IGBT technologies are characterized on an advanced measurement system which is described. The total power losses in the inverter are estimated by simulation at different conditions and it is concluded that the Non Punch Through technology is most useful for higher switching frequencies, while the Punch Through technology is special useful at lower switching frequencies and high load currents. It is also concluded the 60°-PWM modulation has the lowest power losses and the power losses are almost independent of phase angle cos(&phi) for normal motor operation. [5] L. J. Borle and C. V. Nayar, "Zero average current error controlled power flow for ac-dc power converters," IEEE Transactions on Power Electronics, vol. 10, no. 6, pp. 725-732, 1995. Unity and controlled power factor ac-dc power converters require a current control technique with zero average current error (ZACE) in each switching period. Acting on the current error signal alone, a ZACE controlled converter offers complete real and reactive power flow control with negligible low order current harmonics, a narrow switching frequency band, and relative immunity to dc link or ac line voltage harmonics. Slope-generated hysteresis, a new ZACE current control method is introduced. Simulation and experimental results in a three phase converter are presented. [6] S. R. Bowes and P. R. Clark, "Regular-sampled harmonic-elimination pwm control of inverter drives," IEEE Transactions on Power Electronics, vol. 10, no. 5, pp. 521-531, 1995. Novel Harmonic Elimination PWM strategies for drives, uninterruptible power supplies and static power converters have recently been developed using modified Regular-Sampling techniques. These new PWM strategies can be generated on-line in real-time using a simple microprocessor software algorithm, without resorting to the usual time consuming off-line mainframe computer harmonic elimination numerical techniques. These new PWM techniques can be used over the complete voltage/frequency range of the drive up to and including the transition from PWM to Quasi-Square Wave operation. Results from an experimental microprocessor controlled PWM inverter drive are presented to demonstrate and confirm the special feature of the new Regular-Sampled Harmonic Elimination PWM control strategies. [7] I. Budihardjo and P. O. Lauritzen, "Lumped-charge power mosfet model, including parameter extraction," IEEE Transactions on Power Electronics, vol. 10, no. 3, pp. 379-387, 1995. A fundamentally new, physically-based power MOSFET model features continuous and accurate curves for all three interelectrode capacitances. The model equations are derived from the charge stored on two internal nodes and the three external terminals. A straightforward parameter extraction technique uses the standard gate-charge plot or process data and is matched with interelectrode capacitance measurements. Simulations are in excellent agreement with measurements. The model is used to design a snubber for a flyback converter. [8] J. M. Burdio and A. Martinez, "Unified discrete-time state-space model for switching converters," IEEE Transactions on Power Electronics, vol. 10, no. 6, pp. 694-707, 1995. A unified nonlinear state-space model for arbitrary switching converters is presented, which uses discrete-time modeling of switches. Although its compact and powerful notation is valid for all types of switching circuits, perhaps its main application field is power electronics. The proposed model is valid for any electric circuit composed of ideal switches (externally or internally controlled), RLC elements and energy sources. Therefore, the model is general considering semiconductor devices as ideal switches, which are dealt with as discrete-time dynamic systems. Thus the developed model may be either a hybrid continuous-discrete-time one or a full discrete-time one. Moreover, this model is valid as a circuit simulator. [9] D. Casini, M. Marchesoni, and L. Puglisi, "Sliding mode multilevel control for improved performances in power conditioning systems," IEEE Transactions on Power Electronics, vol. 10, no. 4, pp. 453-463, 1995. A novel control technique has been devised to obtain high dynamics responses from a multilevel power conditioning converter. The theory of Variable Structure Control System with sliding mode has been followed, taking into account the several problems that may be encountered in space environments. The analytical study made provides general tools to design ac power conditioning systems destined to any applications. The new control scheme, its mathematical analysis and digital simulation results relevant to a 115 V/400 Hz ac power system are presented and discussed. [10] E. Cerruto, A. Consoli, A. Raciti, and A. Testa, "Robust adaptive controller for pm motor drives in robotic applications," IEEE Transactions on Power Electronics, vol. 10, no. 1, pp. 62-71, 1995. The paper deals with theoretical development and practical implementation of an adaptive speed and position regulator suitable for robotic applications. The proposed adaptive control scheme is characterized by a reduced amount of computation and is based on the Model Reference Adaptive Control approach to compensate the variations of the system parameters, such as inertia and torque constant. A disturbance torque observer is employed to balance the required load torque and reduce the complexity of the adaptive algorithm. Simulation tests of a robotic drive, including an Interior type Permanent Magnet Synchronous (IPMS) motor, are reported in order to compare the proposed control scheme with standard speed and position regulators. Experimental results, obtained from a prototype based on a commercial PC board, are also reported in order to practically evaluate the feasibility and the features of the proposed adaptive control scheme. [11] C. C. Chan, J. Z. Jiang, W. Xia, and K. T. Chau, "Novel wide range speed control of permanent magnet brushless motor drives," IEEE Transactions on Power Electronics, vol. 10, no. 5, pp. 539-546, 1995. This paper presents a novel approach for wide range speed control of permanent magnet (PM) brushless motor drive, including both sinewave and squarewave versions. As compared with conventional flux-weakening control, the approach takes definite advantages that it can be applied to the squarewave PM brushless motor drive directly, and even to the motor drive with negligible mutual inductances between phase windings. Moreover, it is easier to implement than flux-weakening control because no coordinate transformation is needed. The key of this approach is to make use of the transformer EMF in such a way that it weakens the rotational EMF when the motor operate above the base speed, leading to achieve constant-power operation. Computer simulation and experimental results show that the proposed approach works well. [12] D. Y. Chen, F. C. Lee, and G. Carpenter, "Nondestructive rbsoa characterization of igbt's and mct's," IEEE Transactions on Power Electronics, vol. 10, no. 3, pp. 368-372, 1995. Nondestructive evaluation of IGBT's and MCT's are reported and their corresponding RBSOA's established. It was observed that compared to BJT's, IGBT's, and MCT's exhibit very different turn-off breakdown characteristics. Avalanche breakdown of the parasitic transistor accounts for the loss of dynamic voltage blocking capability of both IGBT's and MCT's. [13] J.-F. Chen and C.-L. Chu, "Combination voltage-controlled and current-controlled pwm inverters for ups parallel operation," IEEE Transactions on Power Electronics, vol. 10, no. 5, pp. 547-558, 1995. In this paper the scheme of combination Voltage-Controlled and Current-Controlled PWM inverters for parallel operation of single-phase uninterruptible power supply (UPS) is proposed. The Voltage-Controlled PWM Inverter (VCPI) unit as a master is developed to keep a constant sinusoidal wave output voltage. The Current-Controlled PWM Inverter (CCPI) units are operated as slave controlled to track the distributive current. The power distribution center (PDC) performs the function of distributing the output current of each active unit. In this proposed scheme of parallel operation, each of the units can be designed nearly independent, and the CCPI units do not need a PLL circuit for synchronization. As a result, the parallel operation of UPS is easy to implement and to expand system capacity. For the purpose of illustration, the system, including three single-phase units which operate in parallel, is analyzed and experimental results are given. [14] K. Chen, A. Elasser, and D. A. Torrey, "Soft switching active snubber optimized for igbt's in single switch unity power factor three-phase diode rectifiers," IEEE Transactions on Power Electronics, vol. 10, no. 4, pp. 446-452, 1995. This paper describes a soft switching active snubber for an IGBT operating in a single switch unity power factor three-phase diode rectifier. The soft switching snubber circuit provides zero-voltage turn-off for the main switch. The high turn-off losses of the IGBT due to the current tailing are reduced by zero-voltage switching. This allows the circuit to be operated at very high switching frequencies with regulated dc output voltage, high quality input current and unity input power factor. Simulation and experimental results are included. [15] Q. Chen, F. C. Lee, and M. M. Jovanovic, "Small-signal analysis and design of weighted voltage control for a multiple-output forward converter," IEEE Transactions on Power Electronics, vol. 10, no. 5, pp. 589-596, 1995. The small-signal model for a multiple-output forward converter with weighted voltage control is derived. The effects of the weighting factors on the small-signal behavior are investigated. In addition, the small-signal characteristics of weighted voltage control are compared with the characteristics of a multiple-output converter with coupled output-filter inductors. Finally, the effects of weighted voltage control on the small-signal characteristics of the converter with coupled inductors are examined. Based on the analysis, the design procedure for loop compensation is presented. The small-signal model and the design procedure are verified on an experimental two-output forward converter. [16] B. Choi and B. H. Cho, "Intermediate line filter design to meet both impedance compatibility and emi specifications," IEEE Transactions on Power Electronics, vol. 10, no. 5, pp. 583-588, 1995. This paper presents simple, noniterative, and practical design procedures for intermediate line filters intended for distributed power applications. The design procedures realize a line filter which simultaneously meets both impedance compatibility requirements and EMI specifications. Design examples are given for both single-stage and two-stage filters. [17] J.-W. Choi and S.-K. Sul, "Resonant link bidirectional power converter: Part i - resonant circuit," IEEE Transactions on Power Electronics, vol. 10, no. 4, pp. 479-484, 1995. This paper proposes a novel resonant circuit capable of PWM operation with zero switching losses. The resonant circuit is aimed at providing zero voltage intervals in the dc link of the PWM converter during the required converter device switching periods, and it gives minimum dc bus voltage stresses and minimum peak resonant current. It requires only two additional switches compared to a conventional PWM converter. It is observed that the resonant circuit guarantees the soft switching of all the switching power devices of converters including the switches for resonant operation. Simulation results and experimental results are presented to verify the operating principles. [18] R. W. De Doncker, F. Profumo, M. Pastorelli, and P. Ferraris, "Comparison of universal field oriented (ufo) controllers in different reference frames," IEEE Transactions on Power Electronics, vol. 10, no. 2, pp. 205-213, 1995. The principle of the Universal Field Oriented (UFO) controller, operating in an arbitrary reference frame, is applied to a CRPWM inverter. Due to its high degree of generality the UFO controller is compatible with rotor, stator, and airgap flux field oriented control. The authors compare the stability regions and the steady state performance of these three types of controllers applied to the same machine. The rotor flux based controller has been selected as the basic reference. Digital simulation results are carried out to show that the performance of the complete UFO system, i.e., combined direct and indirect UFO, in a non rotor flux based reference frame leads to a robust high performance drive with no dependency on machine parameters in steady state. [19] L. C. de Freitas, P. Roberto, and C. Gomes, "High-power high-frequency zcs-zvs-pwm buck converter using a feedback resonant circuit," IEEE Transactions on Power Electronics, vol. 10, no. 1, pp. 19-24, 1995. This paper presents a Buck DC-to-DC converter using a novel lossless commutation cell for high switching frequency and high power operation. The proposed cell consists of a main and an auxiliary switches, with ZVS and ZCS switching characteristics, respectively. The converter control using this cell is realized by the PWM technic, with constant switching frequency operation. The complete operation principles, theoretical analysis, relevant equations, state space phase, simulation and experimental results for the Buck converter are presented. [20] A. F. de Souza and I. Barbi, "New zvs-pwm unity power factor rectifier with reduced conduction losses," IEEE Transactions on Power Electronics, vol. 10, no. 6, pp. 746-752, 1995. This paper introduces a new single-phase high power factor rectifier, which features regulation by conventional PWM, soft commutation and instantaneous average line current control. Furthermore, thanks to the use of a single converter, instead of the conventional configuration composed of a four-diode front-end rectifier followed by a boost converter, a significant reduction in the conduction losses is achieved. A prototype rated at 1.6 kW, operating at 70 kHz, with an input ac voltage of 220 Vrms and an output voltage of 400 V<sub>dc</sub> has been implemented in laboratory. An efficiency of 97.8% at 1.6 kW has been measured. Analysis, design, and the control circuitry are also presented in the paper. [21] A. Draou, Y. Sato, and T. Kataoka, "New state feedback based transient control of pwm ac to dc voltage type converters," IEEE Transactions on Power Electronics, vol. 10, no. 6, pp. 716-724, 1995. This paper presents a new state feedback based control strategy for a PWM ac to dc voltage type converter with phase and amplitude control. In this control strategy the state variables of the LC filter connected to the ac side of the converter are fed back to the PWM pattern generator, thereby eliminating a dc offset of the ac input currents as well as oscillations of the dc output current during transients. Computer simulation of the converter system with the proposed control strategy shows that the transient waveforms of ac input and dc output currents are improved greatly even if the damping effect of the ac side resistance can not be expected. The dc voltage regulation with good dynamic response is also achieved even if dc capacitance is substantially reduced. Experimental results from a low power laboratory model are also included to confirm the simulated results and to demonstrate the effectiveness of the proposed control strategy. [22] M. Ehsani, M. O. Bilgic, S. Khan, L. Laskai, and S. G. Jeong, "Capacitor coupled converter (c<sup>3</sup>) for high power dc conversion," IEEE Transactions on Power Electronics, vol. 10, no. 4, pp. 511-518, 1995. The bang-bang controlled capacitor coupled converter (C<sup>3</sup>) is described in this paper. Due to the converter's inherent commutating property, the C<sup>3</sup> can accommodate thyristors as well as high-power gate turn-off switches, due to zero-current switching transitions. The zero-current switching is achieved at no current stress increase, therefore, the topology is considered appropriate for high-power processing. DC and small signal ac models are derived for the bang-bang controlled C<sup>3</sup>, a design procedure is proposed, and simulation results are discussed. Finally, oscillograms from a proof of principle prototype circuit are presented. [23] N. Femia, G. Spagnuolo, and V. Tucci, "State-space models and order reduction for dc-dc switching converters in discontinuous modes," IEEE Transactions on Power Electronics, vol. 10, no. 6, pp. 640-650, 1995. The state-space modeling and related order reduction problems of switching dc-dc converters operating in discontinuous (D) mode are treated in this paper. A unified discrete-time full-order model is proposed assuming the discontinuous current and voltage mode (DCVM) as a general operation mode from which the discontinuous current mode (DCM), the discontinuous voltage mode (DVM), and continuous mode (CM) derive as special cases. Such model permits a straightforward study of the control-to-output response, in each operation mode. The order reduction of the transfer function is carried out by means of the principal component analysis considering the joint controllability and observability properties of the circuit. It is shown that a proper order reduction can be gained not only in DC mode, as expected, but also in DV and DCV modes. A substantial difference between DC and DV modes is also evidenced in terms of controllability. The frequency analysis and state-space model order reduction for a Cuk converter are proposed to show that the method is free of the limitations affecting other methods of analysis and that its predictions fit experimental measurements. [24] C. A. Ferreira, S. R. Jones, B. T. Drager, and W. S. Heglund, "Design and implementation of a five-hp, switched reluctance, fuel-lube, pump motor drive for a gas turbine engine," IEEE Transactions on Power Electronics, vol. 10, no. 1, pp. 55-61, 1995. A new switched reluctance (SR) fuel/lube (F/L) pump system has been developed for a gas turbine engine application. The system is rated at 5 hp, 270 Vdc, 12.5 krpm maximum operating speed, and consists of a SR machine mounted on the F/L pump shaft, an inverter, and an electronic controller. This paper focuses on the design, implementation, and performance of the system. The system can use one of two methods for rotor position sensing, either a resolver or electronic position sensing (EPS). The F/L pump system has undergone extensive performance testing with the resolver. Currently, testing is underway using electronic position sensing. Test results are given to validate the system design and compare the performance using both approaches to position sensing. System efficiency is about 82 percent at full load. [25] J. A. Ferreira, W. A. Cronje, and W. A. Relihan, "Integration of high frequency current shunts in power electronic circuits," IEEE Transactions on Power Electronics, vol. 10, no. 1, pp. 32-37, 1995. Novel geometries are suggested as extensions of shunt design concepts for integrating inexpensive current measurement shunts directly into loads and various other structures. Typical applications would be as high power dissipation loads with low inductance, for use at low voltages where it is necessary to measure current or as permanently installed current sensors. [26] G. Griva, T. G. Habetler, F. Profumo, and M. Pastorelli, "Performance evaluation of a direct torque controlled drive in the continuous pwm-square wave transition region," IEEE Transactions on Power Electronics, vol. 10, no. 4, pp. 464-471, 1995. This paper investigates the operation of a direct torque controlled drive when operating under transient conditions and when operating in overmodulation conditions or in the 'transition region' to six-step operation. The direct torque control is a dead-beat control of the torque and flux magnitude. In the steady-state, the stator voltage vector which drives the torque and flux to the reference value is calculated during each fixed switching period. Under transient or overmodulation conditions, an alternative switching algorithm must be used since dead-beat control is no longer possible. Two alternatives are presented for operation in overmodulation. The first involves a determination of the switching state a priori, and calculating the duty cycle for each phase based on the torque and flux error. A much simpler scheme is presented which utilizes the voltage reference vector from the direct torque control algorithm. This scheme, although not resulting in dead-beat control, is shown to provide very satisfactory performance in overmodulation. The direct torque control method shows great promise for light traction applications where a large quasi-constant power region is required. The scheme operates very satisfactorily in overmodulation, compared with existing current regulated PWM-based schemes, due to the fact that the voltage space vectors are directly controlled. A complete experimental evaluation of the proposed scheme operating in the transition region is also given. [27] W.-J. Gu and K. Harada, "Novel self-excited forward dc-dc converter with zero-voltage-switched resonant transitions using a saturable core," IEEE Transactions on Power Electronics, vol. 10, no. 2, pp. 131-141, 1995. A novel self-excited forward converter is proposed. The turn-on and turn-off of the switch are zero-voltage-switching with resonant transition. A saturable core is used to achieve the self-excitation and the zero-voltage-switched resonant transition. The voltage waveform across the switch is trapezoidal with sinusoidal transitions, and the current waveform flowing through the switch is quasisquare. The switching losses, the conduction losses and the stresses of the switch are significantly reduced in the proposed converter. The output voltage is determined by the ON duty ratio of the switch as in a PWM converter. Two methods to modulate the ON duty ratio are proposed. Both methods results in variable-frequency operation. Experiments on two 5 V, 20 A dc-dc converters show good performance. [28] A. R. Hefner, Jr., "Modeling buffer layer igbt's for circuit simulation," IEEE Transactions on Power Electronics, vol. 10, no. 2, pp. 111-123, 1995. The dynamic behavior of commercially available buffer layer IGBT's is described. It is shown that buffer layer IGBT's become much faster at high voltages than nonbuffer layer IGBT's with similar low voltage characteristics. Because the fall times specified in manufacturers' data sheets do not reflect the voltage dependence of switching speed, a new method of selecting devices for different circuit applications is suggested. A buffer layer IGBT model is developed and implemented into the Saber circuit simulator, and a procedure is developed to extract the model parameters for buffer layer IGBT's. It is shown that the new buffer layer IGBT model can be used to describe the dynamic behavior and power dissipation of buffer layer IGBT's in user-defined application circuits. The results of the buffer layer IGBT model are verified using commercially available IGBT's. [29] S. Hiti and D. Borojevic, "Robust nonlinear control for boost converter," IEEE Transactions on Power Electronics, vol. 10, no. 6, pp. 651-658, 1995. The standard current loop is modified for a boost converter to eliminate sensitivity of the control-to-output transfer function to the nature and magnitude of resistive load. An additional term directly proportional to the load current and output voltage, and inversely proportional to the input voltage is added to the current loop. This results in practically invariant loop gains for different resistive loads, including constant power load. [30] J. Hong, D. Maksimovic, R. W. Erickson, and I. Khan, "Half-cycle control of the parallel resonant converter operated as a high power factor rectifier," IEEE Transactions on Power Electronics, vol. 10, no. 1, pp. 1-8, 1995. A half-cycle control technique for the parallel resonant converter operated as a high power factor rectifier is introduced in this paper. Switching of the bridge power transistors is determined such that the bridge input current averaged over half switching cycle exactly follows the reference proportional to the input voltage. Zero-current switching and below-resonance operation are guaranteed, while control of the input current is the fastest possible, regardless of the operating point. In contrast to conventional regulators, the performance is preserved under both small and large signal variations, and also for large variations of the power-stage parameter values. Fast response, stability and robustness are experimentally verified on a 1.4 kW prototype. [31] C. Hua, "Two-level switching pattern deadbeat dsp controlled pwm inverter," IEEE Transactions on Power Electronics, vol. 10, no. 3, pp. 310-317, 1995. A two-level switching algorithm of the deadbeat controlled PWM inverter is presented. Two levels, instead of three levels, are used in the pulse pattern. This scheme allows the use of higher switching frequency for a given computation time delay, which results in lower total harmonic distortion at the output. Control algorithms are derived. The proposed control scheme is implemented using a TI TMS320C14 DSP controlling an inverter to produce a very low THD sinusoidal output voltage. Simulation and experimental results are presented to verify the performance. [32] J. L. Hudgins, D. W. Bailey, R. A. Dougal, and V. Venkatesan, "Streamer model for ionization growth in a photoconductive power switch," IEEE Transactions on Power Electronics, vol. 10, no. 5, pp. 615-620, 1995. The ionization process in a high gain photoconductive GaAs power switch is explored computationally, based on a streamer model. The streamer velocity was found to increase with increasing electric field, decreasing temperature, or increasing background ionization density. The electric field dependence of streamer velocity is consistent with experimental observations, lending support for the model's predictions about the temperature and background ionization density dependencies. The large electric field associated with the highly charged streamer tip allows virtual propagation of the ionization column at speeds above 10<sup>8</sup> cm/s, well in excess of the carrier saturated drift velocity. [33] S. Y. R. Hui and C. Christopoulos, "Modeling non-linear power electronic circuits with the transmission-line modeling technique," IEEE Transactions on Power Electronics, vol. 10, no. 1, pp. 48-54, 1995. This paper describes a non-linear transmission-line modeling technique that can be employed to model power electronic circuits. The non-linearities that can be dealt with include the switching action of the power devices as well as the non-linear behavior of saturable inductors and multi-layer capacitors. With this new non-linear technique, the transmission-line modeling technique can now be used as a generalized discrete-time modeling tool for power electronic circuits. The non-linear technique is demonstrated in two examples and the simulations are found to be good. [34] H. Huisman, "Multiphase series-resonant converter with a new topology and a reduced number of thyristors," IEEE Transactions on Power Electronics, vol. 10, no. 1, pp. 86-93, 1995. Multiphase series-resonant (SR) power converters provide a flexible way to transform power between a utility grid and a multiphase load or source. The current implementations all suffer from a high component count, which makes the use of these converters unattractive from an economical point of view. A new topology for multiphase SR converters has been proposed in the literature in a simulation context. This topology uses half the number of power semiconductors compared to the existing multiphase SR converters. The present paper addresses the implementation of the new topology in a prototype converter. The old and new topologies are presented. The operation of the new topology is explained. In the new topology the resonant circuit is grounded at one side, which compared to the old topology imposes a restriction on the operation. The paper shows both simulation data and measured waveforms. It is explained that the economical gain due to the reduction in component count is offset by a lower power rating. The paper finishes with conclusions and acknowledgments. Index Terms - Power electronics; control systems; invertors; series resonant converters; three-phase; AC-to-AC power converter; reversible power flow; thyristors; reactive power generation. [35] F. A. Huliehel, W. Tang, F. C. Lee, and B. H. Cho, "Modeling, analysis, and design of the quasi-charge control," IEEE Transactions on Power Electronics, vol. 10, no. 5, pp. 597-604, 1995. A current-mode control technique, the quasi-charge control (QCC), is studied. A small-signal model is developed for the QCC. The model is derived for converters operating in the continuous conduction mode. The model is accurate up to half of the switching frequency. The proposed small-signal model is used to assess the dynamics of the pulse-width-modulated (PWM) converters with QCC, and to compare its performance to the current-injected control (CIC) and charge control (CC) schemes. As in CC, the QCC converges to CIC at light loads close to the boundary between continuous and discontinuous conduction modes. The dynamics of converters with QCC or CC are more sensitive to load change and less sensitive to line change than those of converters with CIC, especially the current loop dynamics. However, unlike in the case of CC, the dependency on the load/line can be controlled when the QCC is designed. Control design guidelines for dc-dc converters and power factor correction rectifiers are presented, and experimental measurements are performed to verify the proposed model. [36] M. Ishida, H. Fujino, and T. Hori, "Real-time output voltage control method of quasi-zcs series resonant hf-linked dc-ac converter," IEEE Transactions on Power Electronics, vol. 10, no. 6, pp. 776-783, 1995. This paper proposes a real-time control method of a series resonant high-frequency linked dc-ac converter employing quasi-zero current switching (quasi-ZCS) and a feedback control method for sinusoidal output voltage. An approximate analysis of the converter is performed, and then simplified equations and an equivalent circuit similar to the conventional PWM inverters/inverters are obtained. A real-time feedback control of the converter is realized using the equivalent circuit without detecting HF link current. The usefulness of the proposed control algorithm is confirmed by experimental results. [37] Y. Ito and S. Kawauchi, "Microprocessor-based robust digital control for ups with three-phase pwm inverter," IEEE Transactions on Power Electronics, vol. 10, no. 2, pp. 196-204, 1995. This study describes a novel method of robust and fast digital control for uninterruptible power supply (UPS) with a three-phase PWM inverter. Results obtained from several experiments indicate that the method offers a total harmonic distortion of 0.62% of the output voltage waveform at a full nonlinear load. Furthermore, the analysis show that the stability of the method is sufficient. [38] D.-H. Jang, G.-H. Choe, and M. Ehsani, "Asymmetrical pwm technique with harmonic elimination and power factor control in ac choppers," IEEE Transactions on Power Electronics, vol. 10, no. 2, pp. 175-184, 1995. This paper describes the asymmetrical pulse with modulated (APWM) control technique for single phase ac choppers, which improves the input power factor and eliminates the harmonics of the output voltage up to a specified order. This technique also enables linear control of the fundamental component of the output voltage. The APWM switching patterns at the specified phase angle are obtained by the Newton-Raphson method and can be implemented by a one-chip microprocessor. Theoretical comparisons are made with conventional PWM technique and the computed performance indicates the superiority of the proposed APWM technique. Practical verification of the theoretical predictions is presented to conform the capabilities of the new technique. [39] A. L. Julian, R. S. Wallace, and P. K. Sood, "Multi-speed control of single-phase induction motors for blower applications," IEEE Transactions on Power Electronics, vol. 10, no. 1, pp. 72-77, 1995. A simple electronic scheme is studied for multi-speed operation of a permanent split capacitor single phase induction motor used to run fractional horsepower blowers and pumps. Computer simulations predict efficiency, harmonic distortion, and pulsating torque when the motor is fed at 60 Hz, 40 Hz or 30 Hz by means of a four-triac bridge circuit. Results of simulations and laboratory tests are compared, showing close agreement. This scheme may be a cost effective alternative to tapped-winding or pole-changing motors. [40] F. Kamran and T. G. Habetler, "Improved deadbeat rectifier regulator using a neural net predictor," IEEE Transactions on Power Electronics, vol. 10, no. 4, pp. 504-510, 1995. This paper proposes a new input current reference prediction scheme for the deadbeat control of a three-phase rectifier used in ac/dc/ac converters. The inherent lag in deadbeat control is compensated predicting the reference resulting in better performance. The proposed predictor consists of a neural net which is trained on-line and predicts the slow varying and periodic trends of the current reference plus a linear first order predictor which predicts the fast variations of the current reference time signal. A CRITIC decides if the neural net training is sufficient and therefore whether or not to use the prediction in the control loop. The learning rule used allows neural net weights to be trained whenever a parameter change causes an increased prediction error. This predictive-regulator is shown to result in improved performance in steady state, in the presence of input voltage imbalance or load variations. [41] S.-J. Kang and S.-K. Sul, "Direct torque control of brushless dc motor with nonideal trapezoidal back emf," IEEE Transactions on Power Electronics, vol. 10, no. 6, pp. 796-802, 1995. In this paper a method of the torque control attenuating the undesired torque pulsation for brushless dc motor with nonideal trapezoidal back EMF is presented. It is the direct torque control method in which the applied output voltage is calculated from the reference torque and the torque of the previous step in the two-phase conducting period and in the commutation period considering the back EMF waveform. The time delay due to the calculation is compensated by the one step ahead current prediction. To measure the instantaneous torque ripple, a torque observer is constructed using a high precision encoder of 50 000 pulse per revolution. The simulation and experimental results show that the proposed method reduces the torque ripple significantly and that it keeps the torque control dynamics as well. [42] H. R. Karshenas, H. A. Kojori, and S. B. Dewan, "Generalized techniques of selective harmonic elimination and current control in current source inverters/converters," IEEE Transactions on Power Electronics, vol. 10, no. 5, pp. 566-573, 1995. This paper presents generalized techniques for realizing PWM patterns which provide selective harmonic elimination and current magnitude modulation, i.e., SHEM, for current source inverters/converters (CSI/C). A combination of chops and short circuit pulses are positioned in such a way that lower order harmonics are eliminated selectively besides current magnitude modulation with minimum switching frequency. Generalized equations and tables which show the relationship of various PWM-SHEM parameters to the position of short circuit pulses and the number of chops per 30° are provided and discussed in detail. [43] N. Kawasaki, H. Nomura, and M. Masuhiro, "New control law of bilinear dc-dc converters developed by direct application of lyapunov," IEEE Transactions on Power Electronics, vol. 10, no. 3, pp. 318-325, 1995. The state space averaging models of Boost, Buck-Boost and Cuk converters are shown to be bilinear systems. Because of the difficulties in analyzing such bilinear systems, most of the previous works dealing with such converters in the state space are confined to the discussions of their linear approximated systems (small signal model). A new control law based on the bilinear large signal models, not linearly approximated, is proposed for achieving the output regulation of these converters. The control law is derived from directly applying the Lyapunov stability theory to the bilinear large signal models, so that the closed loop systems possess excellent output properties, some of which are illustrated by numerical simulations. [44] M. K. Kazimierczuk and M. K. Jutty, "Fixed-frequency phase-controlled full-bridge resonant converter with a series load," IEEE Transactions on Power Electronics, vol. 10, no. 1, pp. 9-18, 1995. A fixed-frequency phase-controlled full-bridge parallel resonant converter (PCPRC) that consists of a phase-controlled parallel resonant inverter (PCPRI) and an input-inductor rectifier is analyzed. The input impedances of the resonant circuits represent inductive loads for both switching legs at f/f<sub>0</sub> gt; 1.24 and therefore zero-voltage-switching turn-on can be achieved for all the transistors. The fundamental frequency approximation is used to derive expressions for the voltage transfer function and the efficiency of the PCPRI. The behavior and performance characteristics of the PCPRI are then studied. Three types of input-inductor rectifiers are considered and a design procedure is developed. A 30-W PCPRC is designed and tested. The theoretical calculations were in good agreement with experimental results. The converter exhibits an excellent efficiency. The measured efficiency was 92% at full load. The converter is capable of regulating the dc output voltage from full load to no load and over a wide line voltage range. [45] R. J. Kerkman, T. M. Rowan, D. Leggate, and B. J. Seibel, "Control of pwm voltage inverters in the pulse dropping region," IEEE Transactions on Power Electronics, vol. 10, no. 5, pp. 559-565, 1995. The overmodulation of pulse width modulated (PWM) inverters causes a nonlinearity in the feedforward channel. The type of modulator, sine wave, space vector, or third harmonic, establishes the characteristics of the transition region's nonlinearity. The characteristics for a number of modulation strategies are introduced. Test results from commercially available volts per hertz (V/F) drives reveal their inability to provide rated voltage even at rated input conditions. The adverse effects of the overmodulation region on current regulated ac inverters are demonstrated by experimental results. A Compensated Modulation Technique (CMT), adaptable to continuous and discontinuous modulators, provides the exact inverse of the nonlinearity; thus it produces a smooth transition to six-step operation without inducing a voltage transient. Experimental results presented in the paper demonstrate the CMT's smooth transition to six-step and the improved performance of the CMT-PWM. Finally, a comparison of the CMT with the other known overmodulation strategy shows the CMT provides a simple technique with essentially identical harmonic characteristics. [46] I. A. Khan, "Synthesis and analysis of transformer-isolated converters," IEEE Transactions on Power Electronics, vol. 10, no. 4, pp. 409-418, 1995. A systematic and straightforward procedure is developed for the synthesis and analysis of transformer-isolated converters. The procedure can be used to determine the ranges of duty-ratio over which the transformer-isolated converters of a given class can be operated without transformer saturation. The procedure can also be used to study the dependence of the converter switch stresses on duty-ratios. This information is useful in the selection of the transformer-isolated converter most suitable for a given application and in the design of this converter with minimum switch stresses, high power density, and low cost. [47] J.-S. Kim and S.-K. Sul, "Resonant link bidirectional power converter: Part ii - application to bidirectional ac motor drive without electrolytic capacitor," IEEE Transactions on Power Electronics, vol. 10, no. 4, pp. 485-493, 1995. This paper proposes a new power converter which consists of two identical 3-phase PWM modulators and a novel resonant circuit. A new control strategy is integrated to realize the bidirectional power converter without an electrolytic link capacitor. The power flow between converters is bidirectional and the regenerative braking is inherent. The source side currents maintain sinusoidal waveforms with a unity power factor. It is observed in the experiment that by balancing the active power between the source and load side, the voltage across a small ceramic link capacitor can be maintained within a small deviation from the reference. Simulation results and experimental results are presented to verify the operational principles. [48] J. W. Kolar, H. Ertl, and F. C. Zach, "Space vector-based analytical analysis of the input current distortion of a three-phase discontinuous-mode boost rectifier system," IEEE Transactions on Power Electronics, vol. 10, no. 6, pp. 733-745, 1995. In this paper the low frequency harmonic distortion of the mains current of a three-phase single-switch discontinuous-mode boost-rectifier is calculated. The system analysis is based on application of space vector calculus and on substitution of discontinuous time shapes within a pulse period by quasicontinuous time shapes. The quasicontinuous time shapes are defined by averaging over the pulse period. The dependency of the shape of the input currents on the voltage transformation ratio is given for various control methods in analytical form. The results of the theoretical analysis are verified by digital simulation and by measurements on a laboratory model. A good consistency of the results has been found. [49] R.-S. Lai and K. D. T. Ngo, "Pwm method for reduction of switching loss in a full-bridge inverter," IEEE Transactions on Power Electronics, vol. 10, no. 3, pp. 326-332, 1995. This paper presents the 'hybrid pulsewidth modulation' (HPWM) method which requires only two of the four switches in a full-bridge inverter to be pulsewidth-modulated at high frequency, thus significantly reducing the switching losses in the other two switches. For triangular carriers, HPWM has the same frequency spectrum and switching losses at the conventional unipolar PWM (UPWM). A low-frequency model for a fast-switching HPWM full-bridge inverter with high-quality output is described, and is substantiated by experimental data. [50] G. Ledwich and P. Doulai, "Multiple converter performance and active filtering," IEEE Transactions on Power Electronics, vol. 10, no. 3, pp. 273-279, 1995. The application of active power filtering to power systems is limited by the low switching rate of available high power inverter switches. In this study, parallel and series connection of multiple voltage source inverter bridges are examined in line with the attempt to increase their effective switching rate. In general, satisfactory results are obtained. [51] R. Li, A. Wallace, and R. Spee, "Determination of converter control algorithms for brushless doubly-fed induction motor drives using floquet and lyapunov techniques," IEEE Transactions on Power Electronics, vol. 10, no. 1, pp. 78-85, 1995. This paper presents a method of analyzing the stability of brushless doubly-fed machines (BDFM) in the synchronous mode of operation. Unlike the stability analysis of conventional induction and synchronous machines for which the linearized state equations are time-invariant, the linearized state equations of the BDFM are time-varying and, consequently, their eigenvalue analysis cannot be performed directly. However, since the system matrix of the linearized equations is a periodic function of time, the generalized theory of Floquet can be applied to transform the time-varying system of equations into an equivalent set of equations with a constant system matrix. Eigenvalue analysis can then be employed to analyze the stability characteristics of given equilibrium points. Investigation into the stability of a proof-of-concept BDFM in the synchronous mode of operation using the transformed linearized model shows good correlation between theoretical and experimental results. In addition, the possibility of designing a BDFM drive with inherent open-loop stability over the entire speed range is demonstrated. Finally, under stable steady state synchronous operation, converter control methods are discussed and it is shown that scalar control methodologies similar to those for induction motor drives can be applied to the BDFM. [52] Y. C. Liang, R. Oruganti, and T. B. Oh, "Design considerations of power mosfet for high frequency synchronous rectification," IEEE Transactions on Power Electronics, vol. 10, no. 3, pp. 388-395, 1995. Synchronous rectifiers used in high frequency, low output voltage applications are power MOSFET's specially designed to replace the usual output Schottky diodes in order to reduce converter losses. This paper deals with the analysis and design optimization of a synchronous rectifier suitable for applications of 1 to 10 MHz switching-mode power supplies. Three different MOSFET structures were studied and evaluated through detailed 2-dimensional device simulations. The internal parameters are optimized against three major performance factors, namely (1) the recovery time of the body diode, (2) the product of on-state resistance and input capacitance, i.e., the loss factor and (3) the breakdown voltage of the body diode. Based on the evaluation, the UMOS structure produces the lowest RC loss factor and the shortest body diode reverse recovery. The final design optimization of the UMOS was then carried out and an optimized device is presented as the final design. [53] C. Licitra, S. Musumeci, A. Raciti, A. U. Galluzzo, R. Letor, and M. Melito, "New driving circuit for igbt devices," IEEE Transactions on Power Electronics, vol. 10, no. 3, pp. 373-378, 1995. IGBT devices are increasingly used in power electronic equipment due to their high power handling capability. This paper deals with the problems that concern the turn-on, turn-off, and short-circuit of these devices. An optimal new driving circuit is proposed which gives excellent device output performances. Experimental oscillogram traces of transient condition tests are given, which demonstrate the advantages of using the new driving circuit. The suitability of the driving circuit for integration is analyzed. [54] H. L. Liu, G. H. Cho, and S. S. Park, "Optimal pwm design for high power three-level inverter through comparative studies," IEEE Transactions on Power Electronics, vol. 10, no. 1, pp. 38-47, 1995. Comparative studies between harmonic elimination and optimal PWM strategies are given for high power three-level inverter feeding induction motor. An effective PWM map construction method based on Valid Region on Frequency Modulation Index Plane is suggested. Thereby, an optimal map including asynchronous space vector PWM, harmonic elimination and optimal PWM method is generated covering all of the low, middle and high modulation index regions. The PWM map was designed for 1 MVA rated general purpose GTO inverter and implemented with digital signal processor. Experimental results are presented for 10 KVA prototype. [55] Y.-F. Liu and P. C. Sen, "Novel method to achieve zero-voltage regulation in buck converter," IEEE Transactions on Power Electronics, vol. 10, no. 3, pp. 292-301, 1995. The Function Control law for Buck converter is derived to achieve zero voltage regulation of the output voltage. A new method to retrieve the low frequency component of the inductor voltage is proposed and analyzed. The stability of the closed loop system using proportional and differential controller is analyzed. The effect of the supply voltage and load current disturbance is also studied. The analysis, computer simulation by PSPICE and experimental results illustrate that excellent performance can be achieved by the Function Control law. [56] Y.-W. Lo and R. J. King, "High performance ripple feedback for the buck unity-power-factor rectifier," IEEE Transactions on Power Electronics, vol. 10, no. 2, pp. 158-163, 1995. The buck unity-power-factor rectifier has harmonic-free input current with complete load regulation down to zero output voltage. A new 'nonlinear ripple feedback' is proposed which exactly cancels the spoiling effect of dc-side current ripple on the low-distortion ac line current waveforms, even for large amounts of ripple. This cancellation is independent of operating point and readily implemented with analog hardware, thereby permitting economies in the design of the dc filter while maintaining harmonic-free operation. Both large-signal and incremental analyses of the rectifier are given. Confirming experimental results from a 1-kW 48-V isolated battery charger operating with current-ripple levels ranging from 50% to discontinuous-conduction-mode operation are given. [57] N. A. Losic, L. D. Varga, and Z. D. Popovic, "Synthesis of zero-admittance converter," IEEE Transactions on Power Electronics, vol. 10, no. 2, pp. 142-147, 1995. A method of synthesizing a system which converts a finite value of an admittance to zero, with associated finite voltage and zero current, is presented. The synthesis method comprises a positive voltage feedback within a negative current feedback. The positive feedback loop incorporates a block of exactly specified nature and value of its transfer function providing for the zero-admittance algorithm. The negative feedback loop controls stability and dynamics of the system. A particular derivation of the zero-admittance converter is applied in synthesizing a load-independent constant-current switch-mode power converter. [58] L. Malesani, L. Rossetto, G. Spiazzi, and P. Tenti, "Performance optimization of cuk converters by sliding-mode control," IEEE Transactions on Power Electronics, vol. 10, no. 3, pp. 302-309, 1995. A novel approach to the design of sliding-mode controllers for Cuk converters is presented, which is valid for both complete state feedback (fourth-order controller) and reduced state feedback (second-order controller). According to the proposed design criteria, both control techniques ensure excellent static and dynamic performances, also resulting in simple control implementation and minimum size of energy transfer capacitor. Experimental results are reported, and compared with those obtained with other popular control techniques. [59] G. Marola, "Quasioptimal on-line control of ac/dc pwm converters," IEEE Transactions on Power Electronics, vol. 10, no. 2, pp. 185-195, 1995. An approximate procedure for on-line computing the loss-optimal values of the switching angles in a class of pulse width modulated converters is presented. The proposed technique is independent of the constants of the circuit and allows to obtain a given power in the dc load with minimum loss of energy in the ac and dc filters. This corresponds to have a quasisinusoidal supply current with minimum ripple on the output load. Simulation and experimental results confirm the practical feasibility of the method. [60] Y. Nakamura, T. Kudo, F. Ishibashi, and S. Hibino, "High-efficiency drive due to power factor control of a permanent magnet synchronous motor," IEEE Transactions on Power Electronics, vol. 10, no. 2, pp. 247-253, 1995. A drive system of a permanent magnet motor without magnetic position detector is described. Generally, the position data of a magnet is obtained from terminal voltage of the motor. In the newly developed method, the inverter dc-link current waveform provides the control signal for driving a permanent magnet motor without a detector. Since the power factor of the motor is controlled around 1.0, the motor runs at a higher efficiency than one controlled by the conventional method. Therefore, this control method saves energy. Current pulsation induced by sudden load fluctuations has been studied and its stabilization has been achieved. This paper provides the principle and operation of the new control method, simulated characteristics, and experimental results. [61] L. R. Nerone, "Mathematical model of the class d converter for compact fluorescent ballasts," IEEE Transactions on Power Electronics, vol. 10, no. 6, pp. 708-715, 1995. The time-harmonic analysis is often used to design the class D converter. Since the Q of the resonant network is often low, this analysis, in the form of the sinusoidal approximation, begins to lose accuracy. This paper explores an improved method of designing compact fluorescent ballasts via the square wave approximation (SWA), where the time domain equations are solved for the general case of arbitrary Q, duty ratio, and frequency. A precise mathematical model of the Class D converter is developed that predicts the currents and voltages of the converter and these solutions are compared with computer simulation. Nonlinear programming (NLP) is introduced as a means to design the ballast for the lowest conduction losses. The equations developed in the mathematical model are formulated into a NLP format that includes the self-oscillating case. [62] K. D. T. Ngo, E. Alpizar, and J. K. Watson, "Modeling of losses in a sandwiched-winding matrix transformer," IEEE Transactions on Power Electronics, vol. 10, no. 4, pp. 427-434, 1995. This paper assesses the suitability of the sandwiched-winding matrix transformer for low-profile applications from the loss standpoint. Finite-element simulations and experiments suggest that the core loss can be adequately characterized by approximating the matrix transformer as a collection of identical uncoupled elements. Thus, a matrix transformer with a large number of elements may have higher core loss than a conventional (tall) transformer, and more core loss than winding loss. Eddy-current analysis reveals that the interconnects which parallel the elements incur a significant fraction of the winding loss. Thus, load distribution is recommended to eliminate the paralleling interconnects in matrix transformers. [63] P. Pejovic and D. Maksimovic, "New algorithm for simulation of power electronic systems using piecewise-linear device models," IEEE Transactions on Power Electronics, vol. 10, no. 3, pp. 340-348, 1995. This paper describes a new algorithm for simulation of power electronic systems. Piecewise-linear approximation is used to model nonlinear components, including switching devices, nonlinear reactive components, and nonlinear control circuitry. A representation of PWL elements is constructed such that a constant system matrix is obtained, regardless of the states of PWL elements. An efficient method for state determination is proposed, which is capable of resolving difficulties caused by discontinuous characteristics of PWL elements. The resulting simulation algorithm is quite general, requires no prior knowledge of the circuit operation, is void of convergence problems, and yields relatively short simulation times on desktop PC machines. [64] D. J. Perreault and J. G. Kassakian, "Effects of firing angle imbalance on 12-pulse rectifiers with interphase transformers," IEEE Transactions on Power Electronics, vol. 10, no. 3, pp. 257-262, 1995. Firing angle or source imbalances between 6-pulse bridges comprising a 12-pulse rectifier lead to current imbalance, due to the finite magnetizing inductance of the interphase transformer. The magnitude of the imbalance is limited by the negative feedback produced by load regulation of the 6-pulse groups. This paper uses both an averaged model and a piecewise-linear simulation to obtain a quantitative understanding of this effect. The averaged model is used to predict steady-state current shifts and transient behavior. The piecewise-linear model of the system is then used to verify and extend the results via computer simulation. It is shown that the current imbalance can be accurately predicted by the averaged model, making the model suitable for both feedback control and interphase transformer design. [65] G. S. N. Raju and S. Doradla, "Lcl resonant converter with pwm control - analysis, simulation, and implementation," IEEE Transactions on Power Electronics, vol. 10, no. 2, pp. 164-174, 1995. A three element resonant converter capable of driving voltage type load with load independent operation is analyzed using state-space approach. Pulse width modulation is employed to control and regulate the output voltage. Closed-form solutions are obtained under steady state conditions. The experimental study of a prototype converter reveals complete agreement with the analytical and SPICE simulation results. Typical experimental oscillograms are given to verify the basic principles. [66] M. Rastogi, N. Mohan, and C. P. Henze, "Three-phase sinusoidal current rectifier with zero-current switching," IEEE Transactions on Power Electronics, vol. 10, no. 6, pp. 753-759, 1995. This paper presents the application of zero-current switching in a three-phase rectification scheme with nearly sinusoidal line currents. The principle of third harmonic current circulation is used to reduce the distortion in the line currents. Zero-current switching is accomplished with the use of only two switches. The operation of the circuit is verified experimentally. Comparisons with a PWM based rectifier and a six-switch rectifier in terms of component stresses and EMI filter considerations are presented. [67] R. Rojas, T. Ohnishi, and T. Suzuki, "Improved voltage vector control method for neutral-point-clamped inverters," IEEE Transactions on Power Electronics, vol. 10, no. 6, pp. 666-672, 1995. A new PWM method for Neutral-Point-Clamped (NPC) inverters is introduced. The method is based on closed-loop control of the line-to-line voltage vectors. It uses independent hysteresis comparator controllers to regulate the direct and quadrature axis components of the three phase output voltages. The controllers select the appropriate output voltage-vector through an EPROM table. The closed-loop control allows a high performance over the whole range of operation, even when low speed devices such as the GTO are used. A neutral-point potential control is described, which is capable of stabilizing the variations within fixed limits during steady and transient states. The principle of the method is discussed and the vector selection technique is presented. The effectiveness in the output-voltage-waveform generation and the balance of the DC-link capacitor voltages are verified by simulation and experiment. [68] R. Scheich and J. Roudet, "Emi conducted emission in the differential mode emanating from an scr: Phenomena and noise level prediction," IEEE Transactions on Power Electronics, vol. 10, no. 2, pp. 105-110, 1995. This paper deals with an EMC analysis of a power converter. In particular, the phenomena and modeling of conducted noise emission caused by an SCR are described. Theoretical results in the time as well as frequency domain are discussed and compared to the time signal measured and its spectrum. [69] J. Sebastian, J. A. Cobos, J. M. Lopera, and J. Uceda, "Determination of the boundaries between continuous and discontinuous conduction modes in pwm dc-to-dc converters used as power factor preregulators," IEEE Transactions on Power Electronics, vol. 10, no. 5, pp. 574-582, 1995. The determination of the boundaries between both modes of conduction (continuous and discontinuous) in PWM dc-to-dc switching converters used as power factor preregulators (PFP) is presented in this paper. When a dc-to-dc switching converter works as a power factor preregulator, its operating point is constantly changing due to the fact that both the dc voltage conversion ratio and the load 'seen' by the converter are constantly changing in each half-sinusoid of the line voltage (input voltage of the converter). In these conditions, the conduction mode cannot be directly determined. In this paper, the boundaries between both conduction modes in each angle of the half-sinusoidal input voltage have been determined. The conditions to always operate in continuous or in discontinuous conduction modes have been determined as well. Finally, these results have been verified by simulations and experimental results. [70] J. Sebastian and J. Uceda, "Alternative method for controlling two-output dc-to-dc converters using saturable core inductor," IEEE Transactions on Power Electronics, vol. 10, no. 4, pp. 419-426, 1995. The method proposed in this paper is an alternative to the use of a conventional magnetic amplifier in the control of a second output in buck derived dc-to-dc converters. This method avoids the use of linear devices in the magnetic amplifier and improves the converter dynamic response. It is very simple and it is based on the use of a saturable core and in the double switching frequency and duty cycle modulation in the power transistor. [71] T. Senjyu and K. Uezato, "Stability analysis and suppression control of rotor oscillation for stepping motors by lyapunov's direct method," IEEE Transactions on Power Electronics, vol. 10, no. 3, pp. 333-339, 1995. Stepping motors are used as the driver for positioning in control systems. It is well-known that the transient response of a stepping motor is generally oscillatory in the case of open-loop control. The rotor oscillation must be suppressed in quick positioning applications. In this paper, the stability analysis and the suppression control of rotor oscillations of variable reluctance stepping motors are studied by Lyapunov's direct method. Since the motor is a nonlinear system, the method is useful to analyze the stability of the motor. The suppression control of rotor oscillations is achieved by excitation control of phase windings using Lyapunov function. The validity of this method is examined by experiments. [72] T. Senjyu, K. Uezato, and H. Miyazato, "Adjustable speed control of ultrasonic motors by adaptive control," IEEE Transactions on Power Electronics, vol. 10, no. 5, pp. 532-538, 1995. The driving principle of the ultrasonic motor (USM) is different from those of the electro-magnetic type motors. Some mathematical models for the USM have been reported in recent years; however, these models are very complex to apply for speed control of the USM. Therefore, the speed controllers have been designed using PI controllers or fuzzy controllers and it is necessary to develop a simple and convenient mathematical model for the USM in order to achieve a high-performance speed control. In this paper, a mathematical model for the USM is proposed which is simple and useful for speed control. The speed controller is designed based on the model using adaptive control theory. Adaptive control is attractive for control of the USM because the speed characteristics of the USM vary with drive conditions. The application of this control scheme to speed control for the USM is attempted first. The effectiveness of proposed control is demonstrated by experiments. [73] S. Singer, D. Shmilovitz, Y. Ifrah, and I. Cohen, "Transmission line based energy recovery circuits and their application in copper vapor laser systems," IEEE Transactions on Power Electronics, vol. 10, no. 2, pp. 239-246, 1995. Energy recovery of narrow, high power pulses based on loss free resistor topology is described. A novel regenerative snubber realization based on transmission lines is presented. The purpose of this snubber is to recycle high voltage, high power (up to 20 KV, 1 MW) parasite pulses which arise in a copper vapor laser. These pulses consume up to 40% of the total power of the system. Currently, a low voltage (170 V) circuit of this type has been constructed and operated at recycling efficiency up to 85%. [74] S. Sivakumar, K. Natarajan, and R. Gudelewicz, "Control of power factor correcting boost converter without instantaneous measurement of input current," IEEE Transactions on Power Electronics, vol. 10, no. 4, pp. 435-445, 1995. This paper proposes a new control method for the constant-frequency control of power factor correcting boost converter using a sinewave template modulated PWM signal which eliminates the need for instantaneous measurement of the line current for the switching control of the boost converter. The control strategy is based on the notion that the line current can be forced to trace a deterministic waveform such as a sinusoid by considering the implicit model of the sinewave in the boost converter controller structure. The modulating sinewave template is generated using the line voltage, the boost converter output voltage and the load current. The paper provides the analysis and the design of the controller and presents simulation and implementation results to demonstrate its effectiveness. [75] K. M. Smedley and S. Cuk, "Dynamics of one-cycle controlled cuk converters," IEEE Transactions on Power Electronics, vol. 10, no. 6, pp. 634-639, 1995. One-Cycle Control is a nonlinear control method. The Flow-Graph modeling technique is employed to study the large-signal and small-signal dynamic behavior of One-Cycle Controlled switching converters. Systematic design method for One-Cycle Control systems is provided with the Cuk converter as an example. Physical insight is given which explains how One-Cycle Control achieves instant control without infinite loop gain. Experimental results demonstrate that a Cuk converter with One-Cycle Control rejects the power source perturbation in one-cycle and the average of the diode voltage follows the control reference in one cycle. [76] K. M. Smedley and S. Cuk, "One-cycle control of switching converters," IEEE Transactions on Power Electronics, vol. 10, no. 6, pp. 625-633, 1995. A new large-signal nonlinear control technique is proposed to control the duty-ratio d of a switch such that in each cycle the average value of a switched variable of the switching converter is exactly equal to or proportional to the control reference in the steady-state or in a transient. One-Cycle Control rejects power source perturbations in one switching cycle; the average value of the switched variable follows the dynamic reference in one switching cycle; and the controller corrects switching errors in one switching cycle. There is no steady-state error nor dynamic error between the control reference and the average value of the switched variable. Experiments with a constant frequency buck converter have demonstrated the robustness of the control method and verified the theoretical predictions. This new control method is very general and applicable to all types of pulse-width-modulated, resonant-based, or soft-switched switching converters for either voltage or current control in continuous or discontinuous conduction mode. Furthermore, it can be used to control any physical variable or abstract signal that is in the form of a switched variable or can be converted to the form of a switched variable. [77] M. C. Smit, J. A. Ferreira, J. D. Van Wyk, and M. Ehsani, "Ultrasonic series resonant converter with integrated l-c-t," IEEE Transactions on Power Electronics, vol. 10, no. 1, pp. 25-31, 1995. The concept of an integrated structure for the capacitor, inductor and transformer of the series resonant converter is presented. It is shown that the necessary capacitance can be achieved by using a bifilar primary and the leakage inductance of the transformer replaces the physical inductor. By integrating three components into one it would be possible to save space, mass, volume and cost. [78] A. M. Stankovic, G. C. Verghese, and D. J. Perreault, "Analysis and synthesis of randomized modulation schemes for power converters," IEEE Transactions on Power Electronics, vol. 10, no. 6, pp. 680-693, 1995. After establishing that the proper objects of study for randomized modulation of converters are the power spectra of signals, we classify such modulation schemes and present associated spectral formulas, several of which are new. We also discuss numerical (Monte Carlo) verification issues for power spectral formulas. A general spectral formula for stationary randomized modulation schemes is presented, and specialized to several modulation schemes of practical interest for dc/dc converters. Analytical results are then given for block-stationary randomized modulation schemes that are suitable for inverter operation. In the process, we present results for several modulation schemes that have been reported in the literature without analytical explanations. Experimental verifications of some of our analytical results are presented. We formulate narrow-band and wide-band synthesis problems in randomized modulation, and solve them numerically. Our results suggest that randomized modulation is very effective in satisfying narrow-band power constraints, but has limited effectiveness in meeting wide-band constraints. [79] W. Sulistyono and P. Enjeti, "Series resonant ac-to-dc rectifier with high-frequency isolation," IEEE Transactions on Power Electronics, vol. 10, no. 6, pp. 784-790, 1995. In this paper, a new series resonant ac-to-dc rectifier with high-frequency isolation is introduced. The proposed approach employs a PWM controlled ac controller, a series resonant tank and a high-frequency isolation transformer. With this approach, the single phase input ac is directly processed via the ac-to-ac converter eliminating the ac-to-dc rectification stage present in the conventional system. The output of the HF transformer is rectified and processed via a filtering stage to obtain a dc output. With the addition of an input filter, the input current is near sinusoidal at unity power factor. Simulation and experiment results are presented to verify the basic concept. [80] F. D. Tan and R. D. Middlebrook, "Unified model for current-programmed converters," IEEE Transactions on Power Electronics, vol. 10, no. 4, pp. 397-408, 1995. A unified model is established for a current-programmed converter, which is both a modification and an extension of familiar models. Inclusion of the sampling effect allows the presence of an additional pole ω<sub>p</sub> in the current-loop gain to be derived. The resulting final double-slope asymptote is fixed in position, and the crossover frequency cannot exceed half the switching frequency. A stability parameter, Q<sub>s</sub>, determines the additional pole and describes the degree of peaking in the closed-loop transfer function. Experimental verification employs an analog signal injection technique. [81] F. D. Tan, J. L. Vollin, and S. M. Cuk, "Practical approach for magnetic core-loss characterization," IEEE Transactions on Power Electronics, vol. 10, no. 2, pp. 124-130, 1995. A practical approach for magnetic core-loss characterization up to a few megahertz is presented. An error analysis is for the first time performed, revealing that corrections are needed to compensate for errors introduced by the extra phase shift inherent in a measurement setup, and by shunt parasitic capacitance associated with an inductive device under test. A simple technique is then proposed to control the error so as to satisfy prescribed tolerances. Extensive measurements done on a TDK PC40 core yield results which support the analysis. Several sample cores are then characterized at a few megahertz. [82] Y. Tang and L. Xu, "Flexible active and reactive power control strategy for a variable speed constant frequency generating system," IEEE Transactions on Power Electronics, vol. 10, no. 4, pp. 472-478, 1995. Variable-speed constant-frequency generating systems are used in wind power, hydro power, aerospace, and naval power generations to enhance efficiency and reduce friction. In these applications, an attractive candidate is the slip power recovery system comprising of doubly excited induction machine or doubly excited brushless reluctance machine and PWM converters with a dc link. In this paper, a flexible active and reactive power control strategy is developed, such that the optimal torque-speed profile of the turbine can be followed and overall reactive power can be controlled, while the machine copper losses have been minimized. At the same time, harmonics injected into the power network has also been minimized. In this manner, the system can function as both a high-efficient power generator and a flexible reactive power compensator. [83] D. A. Torrey and A. M. A. M. Al-Zamel, "Single-phase active power filters for multiple nonlinear loads," IEEE Transactions on Power Electronics, vol. 10, no. 3, pp. 263-272, 1995. An active power filter based on a single-phase inverter is proposed for single-phase systems. Issues such as the background on the operation of the filter, details of the power circuit, control design, representative waveforms as well as the spectral performance of a filter supporting a 384 W ac controller and a 900 W uncontrolled bridge rectifier are addressed. Experimental data suggest that the active filter typically consumes 3% or less of the average load power. The spectral performance indicate that the active filter brings the system into compliance with IEC-555 for decision frequencies in excess of 30 kHz. Additionally, a discussion outlining an alternative single-phase active filter is presented. [84] C. K. Tse, S. C. Wong, and M. H. L. Chow, "On lossless switched-capacitor power converters," IEEE Transactions on Power Electronics, vol. 10, no. 3, pp. 286-291, 1995. This paper addresses the design of efficient switched-capacitor power converters. The discussion starts with a review of the fundamental limitation of switched-capacitor circuits which shows that the topology of such circuits and the 'forced' step changes of capacitor voltages are the inherent attributes of power loss. Although the argument follows from a rather trivial result from basic circuit theory, it addresses an important issue on the maximum efficiency achievable in a switched-capacitor converter circuit. Based on the observed topological constraint of switched-capacitor converter circuits, the simplest lossless topology for AC/DC conversion is deduced. Also discussed is a simple version of lossless topology that achieves isolation between the source and the load. Finally, an experimental AC/DC switched-capacitor converter, based on the proposed idea, is presented which demonstrates an improved efficiency over other existing switched-capacitor converters. The proposed AC/DC converter contains no inductors and thus is suitable for custom IC implementation for very low power applications. [85] Y.-Y. Tzou and H.-J. Wu, "Lqg/ltr control of an ac induction servo drive," IEEE Transactions on Power Electronics, vol. 10, no. 2, pp. 214-221, 1995. A new design method based on the linear-quadratic-Gaussian with loop-transfer-recovery (LQG/LTR) theory has been developed for the design of high performance ac induction servo drives using microcomputer-based digital control. The principle of field orientation is employed to achieve the current decoupling control of an induction motor. An equivalent model representing the dynamics of the decoupled induction motor has been developed. Based on the developed model with specified parameter uncertainties and given performance specifications, a frequency domain loop-gain-shaping method based on the LQG/LTR theory is proposed for the design of the servo loop controller. A microcomputer-based induction servo drive has been constructed to verify the proposed control scheme. Simulation and experimental results are given to illustrate the effectiveness of the proposed design method. [86] F. Ueda, K. Matsui, M. Asao, and K. Tsuboi, "Parallel-connections of pulsewidth modulated inverters using current sharing reactors," IEEE Transactions on Power Electronics, vol. 10, no. 6, pp. 673-679, 1995. A technique of parallel connection of power devices by using current sharing reactors for pulsewidth modulated (PWM) inverters is reported in this paper. The proposed technique not only increases the current capacity but also decreases the output harmonic contents. The output voltage waveforms of the proposed inverter have certain voltage levels during their half cycles, thus it is anticipated that it will be difficult to analyze the output waveforms. For such waveforms, a frequency analysis approach is described, whose results are verified by experiments. [87] S. S. Valtchev, J. B. Klaassens, and M. P. N. van Wesenbeeck, "Super-resonant converter with switched resonant inductor with pfm-pwm control," IEEE Transactions on Power Electronics, vol. 10, no. 6, pp. 760-765, 1995. The efficiency of the series-resonant power converters is proved to increase with the improvement of the current form factor of the resonant current. The application of `soft-switching' is reducing the switching losses. The maximum value for the pulse frequency in a super-resonant converter is limited by the introduction of a method of pulse width modulation. To improve the current form factor a second inductance is placed in the output side of the converter. This inductance is alternately included in the resonant circuit. The paper offers graphical presentation of the characteristics made to select the choice of the best suitable relationship between the resonant and output inductances and to support the design. The role of the parasitic elements of a transformer is specified. [88] E. van Dijk, H. J. N. Spruijt, D. M. O'Sullivan, and J. B. Klaassens, "Pwm-switch modeling of dc-dc converters," IEEE Transactions on Power Electronics, vol. 10, no. 6, pp. 659-665, 1995. The introduced PWM-switch modeling method is a simple method for modeling pulse-width-modulated (PWM) dc-dc converters operating in the continuous conduction mode. The main advantage of this method is its versatility and simple implementation compared to other methods. The basic idea is the replacement of the switches in the converter by their time-averaged models. These switch models have been developed in such a way that the converter model provides the same results as the state-space-averaging technique but now including nonlinear effects. Simple rules for determination of the switch models are obtained. The resulting model is a time-averaged equivalent circuit model where all branch currents and node voltages correspond to their averaged values of the corresponding original currents and voltages. The model also includes parasitics, second-order effects and nonlinearities, and can be implemented in any circuit-oriented simulation tool. The same model is used for the simulation of the steady-state and the transient behavior. [89] V. Vlatkovic, D. Borojevic, and F. C. Lee, "Zero-voltage switched, three-phase isolated pwm buck rectifier," IEEE Transactions on Power Electronics, vol. 10, no. 2, pp. 148-157, 1995. A novel three-phase, single-stage, isolated PWM rectifier is proposed, which is capable of achieving unity power factor, and low harmonic distortion of input currents, and in the same time realizing zero-voltage switching for all power semiconductor devices. Operation of the proposed circuit is thoroughly analyzed. Design equations and trade-offs are provided. The performance of the proposed circuit is demonstrated through a 2 kW, 100 kHz, digital signal processor controlled prototype. The conversion efficiency is around 93%. [90] S. N. Vukosavic and M. R. Stojic, "Reduction of parasitic spectral components of digital space vector modulation by real-time numerical methods," IEEE Transactions on Power Electronics, vol. 10, no. 1, pp. 94-102, 1995. This paper presents the analysis of the voltage error caused by a finite resolution of the modulator. The suitable algorithm is proposed in order to eliminate offsets and to reduce parasitic components for as much as 15 dB. Essentially, the algorithm represents the numerical procedure of rounding the high-resolution amplitude products into lower resolution digital words that are to be loaded into the PWM counters. For a given resolution of the modulator, the suggested procedure considers the coupling between the phase residual errors and selects counter loads in such a way that the minimum voltage vector error is obtained. The presented analytical considerations are verified by experimental results. The spectra of the inverter output voltage, obtained in an experimental setup, illustrate the efficiency of the proposed algorithm in suppressing undesired spectral components of the inverter output. [91] C. M. Wildrick, F. C. Lee, B. H. Cho, and B. Choi, "Method of defining the load impedance specification for a stable distributed power system," IEEE Transactions on Power Electronics, vol. 10, no. 3, pp. 280-285, 1995. By applying the loop gain analysis technique, a forbidden region for the polar plot of the ratio of impedances at the interface between two cascaded subsystems is determined. A method of transforming the forbidden region into a load impedance specification for a given source impedance is developed. The method assures system stability and minimal performance degradation of the distributed power system, while allowing impedance overlap at the interface. [92] A. F. Witulski, "Introduction to modeling of transformers and coupled inductors," IEEE Transactions on Power Electronics, vol. 10, no. 3, pp. 349-357, 1995. A tutorial paper is presented on modeling and design of transformers and coupled inductors. Beginning with a brief review of electromagnetic laws and magnetic circuit models, the magnetic and electric models of transformers and coupled inductors are developed, including both magnetizing and leakage effects. It is shown that while the voltage waveforms on the windings are primarily related by the turns ratio for both devices, the winding currents of transformers and coupled inductors are determined by very different mechanisms. An integrated structure with both transformer and coupled inductor on the same core is also discussed, as well as the special case of the coupled inductor used on a multiple-output transformer-isolated converter. [93] S.-C. Wong and A. D. Brown, "Analysis, modeling, and simulation of series-parallel resonant converter circuits," IEEE Transactions on Power Electronics, vol. 10, no. 5, pp. 605-614, 1995. This paper presents a SPICE macromodel for a generic series-parallel resonant converter circuit. The model is derived from the averaged time-invariant state-space equations obtained from a Fourier transform. The conditions are derived under which all but the fundamental harmonic may be discarded, and the model developed based solely on the fundamental Fourier component. The single macromodel developed has a wide range of validity, and allows dc, ac, and transient analyses to be carried out in a fast, easy, and familiar manner. It also permits the converter to be incorporated alongside its control circuitry into an entire system. The simulation results from the model have been compared to results from a full simulation, and the agreement is found to be excellent, with the macromodel simulation running between 37 and 4700 times faster than the full simulation. [94] J. G. Zhu, S. Y. R. Hui, and V. S. Ramsden, "Dynamic equivalent circuit model for solid magnetic cores for high switching frequency operations," IEEE Transactions on Power Electronics, vol. 10, no. 6, pp. 791-795, 1995. This paper presents a dynamic equivalent circuit model of solid magnetic cores for high frequency operations in power electronic circuits. The effects of eddy current, domain wall motion, and hysteresis are taken into account by distributed equivalent resistors and distributed nonideal differential inductors, respectively. The Preisach hysteresis model is employed to simulate hysteresis effects in the inductors. A recently developed discrete transform technique based on the transmission line method is adopted to develop a discrete model for numerical dynamic analysis. The resultant model is just a simple tridiagonal system of equations. Good agreement between computer simulations and measurements has confirmed the validity of the new model.